Hi
I have the idea to use a combination of use and source filter as safe syntactic macro mechanism like in LISP.
(well a poor mans version but still better than the alternatives which try to parse Perl)
The following code injects the new code at compile time into the line after the use statement.
My problem is that statements in the same line following the use are skipped, before the insert starts.
Any idea if this can be fixed?
Probably by manipulating the DATA filehandle reading the source?
Sample code implements an inlined SWAP of two variables.
>> cat exp/t_inject.pl
use lib '../lib';
my ($x,$y);
BEGIN {($x,$y)=(0,42)}
use Filter::Inject $x,$y; warn "after same line";
warn "+1 line";
warn "+2 line";
warn "$x $y";
Output shows variables have been swapped, but inlining happens after the lines end (not the statements end, see mark)
$ perl t_inject.pl
IMPORT(Filter::Inject 0 42) at ../lib/Filter/Inject.pm line 46.
after same line at t_inject.pl line 6. <---
--- START MACRO swap at t_inject.pl line 9.
--- END MACRO swap at t_inject.pl line 14.
+1 line at t_inject.pl line 7.
+2 line at t_inject.pl line 8.
42 0 at t_inject.pl line 9.
(please note, while the inject sub is only hardcode to simplify the demonstration, the full scale version creates pseudo modules with own macros on the fly, which can be called as use swap $x,$y )
please ignore the Module-starter boilerplate
>> cat lib/Filter/Inject.pm
package Filter::Inject;
use 5.006;
use strict;
use warnings FATAL => 'all';
=head1 NAME
Filter::Inject - The great new Filter::Inject!
=head1 VERSION
Version 0.02
=cut
our $VERSION = '0.02';
=head1 SYNOPSIS
Quick summary of what the module does.
Perhaps a little code snippet.
use Filter::Inject;
my $foo = Filter::Inject->new();
...
=head1 EXPORT
A list of functions that can be exported. You can delete this section
if you don't export anything, such as for a purely object-oriented mod
+ule.
=cut
package Filter::Inject ;
use Filter::Util::Call ;
sub import {
warn "IMPORT(@_)";
my $package = shift;
my $inject = inject(@_);
# adjust line number to disguise injection
my ($file,$line) = (caller)[1,2];
$line++;
$inject .= qq{\n# line $line "$file"\n};
filter_add(
sub
{
my $status = filter_read_exact(1);
if ( $status > 0) {
$_= $inject .";".$_;
filter_del();
}
$status ;
}
)
}
sub inject {
local $"=',';
package swap;
our $args = \@_;
return q{
{
warn "--- START MACRO swap";
package swap; our $args;
my $tmp = $args->[0];
$args->[0] = $args->[1];
$args->[1] = $tmp;
warn "--- END MACRO swap";
}
}
}
1 ;
=head1 AUTHOR
Rolf Michael Langsdorf, C<< <lanxperl at gmail.com> >>
=head1 BUGS
Please report any bugs or feature requests to C<bug-filter-inject at r
+t.cpan.org>, or through
the web interface at L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=
+Filter-Inject>. I will be notified, and then you'll
automatically be notified of progress on your bug as I make changes.
=head1 SUPPORT
You can find documentation for this module with the perldoc command.
perldoc Filter::Inject
You can also look for information at:
=over 4
=item * RT: CPAN's request tracker (report bugs here)
L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=Filter-Inject>
=item * AnnoCPAN: Annotated CPAN documentation
L<http://annocpan.org/dist/Filter-Inject>
=item * CPAN Ratings
L<http://cpanratings.perl.org/d/Filter-Inject>
=item * Search CPAN
L<http://search.cpan.org/dist/Filter-Inject/>
=back
=head1 ACKNOWLEDGEMENTS
=head1 LICENSE AND COPYRIGHT
Copyright 2018 Rolf Michael Langsdorf.
This program is free software; you can redistribute it and/or modify i
+t
under the terms of the the Artistic License (2.0). You may obtain a
copy of the full license at:
L<http://www.perlfoundation.org/artistic_license_2_0>
Any use, modification, and distribution of the Standard or Modified
Versions is governed by this Artistic License. By using, modifying or
distributing the Package, you accept this license. Do not use, modify,
or distribute the Package, if you do not accept this license.
If your Modified Version has been derived from a Modified Version made
by someone other than you, you are nevertheless required to ensure tha
+t
your Modified Version complies with the requirements of this license.
This license does not grant you the right to use any trademark, servic
+e
mark, tradename, or logo of the Copyright Holder.
This license includes the non-exclusive, worldwide, free-of-charge
patent license to make, have made, use, offer to sell, sell, import an
+d
otherwise transfer the Package with respect to any patent claims
licensable by the Copyright Holder that are necessarily infringed by t
+he
Package. If you institute patent litigation (including a cross-claim o
+r
counterclaim) against any party alleging that the Package constitutes
direct or contributory patent infringement, then this Artistic License
to you shall terminate on the date that such litigation is filed.
Disclaimer of Warranty: THE PACKAGE IS PROVIDED BY THE COPYRIGHT HOLDE
+R
AND CONTRIBUTORS "AS IS' AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES
+.
THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE, OR NON-INFRINGEMENT ARE DISCLAIMED TO THE EXTENT PERMITTED BY
YOUR LOCAL LAW. UNLESS REQUIRED BY LAW, NO COPYRIGHT HOLDER OR
CONTRIBUTOR WILL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, OR
CONSEQUENTIAL DAMAGES ARISING IN ANY WAY OUT OF THE USE OF THE PACKAGE
+,
EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
=cut
1; # End of Filter::Inject
